1. Field of the Invention
The present invention generally relates to wireless communications and more particularly to changing radio frequency (RF) emission patterns with respect to one or more antenna arrays.
2. Description of the Related Art
In wireless communications systems, there is an ever-increasing demand for higher data throughput and a corresponding drive to reduce interference that can disrupt data communications. A wireless link in an Institute of Electrical and Electronic Engineers (IEEE) 802.11 network may be susceptible to interference from other access points and stations, other radio transmitting devices, and changes or disturbances in the wireless link environment between an access point and remote receiving node. The interference may degrade the wireless link thereby forcing communication at a lower data rate. The interference may, in some instances, be sufficiently strong as to disrupt the wireless link altogether.
One solution is to utilize a diversity antenna scheme. In such a solution, a data source and intermediate RF generating device are coupled to two or more physically separated omnidirectional antennas. An access point may select one of the omnidirectional antennas by which to maintain a wireless link. Because of the separation between the omnidirectional antennas, each antenna experiences a different signal environment and corresponding interference level with respect to the wireless link. A switching network couples the intermediate RF generating device and corresponding data source to whichever of the omnidirectional antennas experiences the least interference in the wireless link.
Many methods that provide for switching among antenna configurations, such as diversity antennas, and other methods of controlling antenna segments fail to effectively minimize the interference from other access points, other radio transmitting devices, or disturbances in the environment of the wireless link between the access point and the remote receiving node. Methods for antenna configuration selection are typically by trial-and-error.
In such a trial-and-error approach, a transmission is made on each antenna configuration to determine which antenna configuration provides a more effective wireless link as might be measured by a packet error ratio. The trial-and-error approach is inefficient as it generally requires transmission on a “bad” antenna configuration to determine the particularities of the poor quality of that antenna configuration. Further, as the transmitting or receiving device move around, new sources of interference arise to degrade a transmission. The trial-and-error approach therefore becomes increasingly inefficient with a large number of antenna configurations and devices that may have adjustable positions.
FIG. 1 is a block diagram of a wireless device 110 in communication with one or more remote recipient device and as is generally known in the prior art. While not shown, the wireless device 110 of FIG. 1 includes an antenna apparatus, an RF transmitter and/or a receiver, which may operate using the 802.11 protocol. The wireless device 110 of FIG. 1 may be illustrative of a set-top box, a laptop computer, a television, a PCMCIA card, a remote control, a cellular telephone, a handheld gaming device, or a remote terminal.
The wireless device 110 may be a handheld device that receives input through an input mechanism configured to be used by a user. The wireless device 110 may then process the input and generates an RF signal. The generated RF signal may then be transmitted to one or more nodes 120, 130 and 140 via wireless links. Nodes 120-140 may receive data, transmit data, or transmit and receive data (i.e., a data transceiver).
Wireless device 110 may also be an access point for communicating with one or more remote receiving nodes over a wireless link as might occur in an 802.11 wireless network. The wireless device 110 may receive data from a router connected to the Internet (not shown). The wireless device 110 may then convert and wirelessly transmit the data to one or more remote receiving nodes (e.g., receiving nodes 120-140). The wireless device 110/access point may also receive a wireless transmission from one of the nodes 120-140 convert the data and allow for transmission of that data over the Internet via the aforementioned router. The wireless device 110 may also form a part of a wireless local area network (LAN) that allows for communications among two or more of nodes 120-140. For example, node 140, which may be a cellular phone with WiFi capability, may communicate with node 120, which may be a laptop computer including a WiFi card or chip with wireless capabilities. Those communications may be routed through the wireless device 110, which creates the wireless LAN environment.
Wireless device 110 may be placed in different positions on a wall, desk, or in conjunction with another structure. The radiation pattern emitted by the wireless device 110 may then be based on the detected position of the device. A radiation pattern that extends in a horizontal manner from the wireless device 110 may be desirable for a device mounted flat against a ceiling of room or on a central table-like surface. Alternatively, when the device is mounted on its side and against a wall, a radiation pattern may extend outward in a vertical manner from the wireless device 110. Such an arrangement may be desirable if one or more nodes 120-140 are attempting to interact with an access point (wireless device 110) on different floors of a building.
Arranging wireless access points or other wireless devices in such a manner may require the party responsible for installation of wireless device 110 to ensure that it is properly configured for a horizontal and/or vertical wireless transmission. This is especially true with prior art wireless devices and access points that tend to transmit only in one-dimension. The particulars of any given radiation pattern generated by a wireless device may be not be immediately apparent to an individual charged with creating a wireless network but otherwise lacking extensive knowledge into RF emission patterns. Further difficulties might arise with respect to intermediate arrangements of the wireless device (e.g., at a 45 degree angle).
The problems associated with radiation patterns become even more apparent with respect to mobile devices, especially cellular phones or mobile devices with WiFi capability. Such devices are constantly in motion and may at one moment be on a horizontal plane with an access point and a few moments later be vertical to the access point. The angle of a mobile device vis-a-vis the access point may change in as a little as a few seconds as a user may walk around an office or even bring the device from their desktop up to their ear as they stand at their desk.
There is a need in the art for adjusting antenna patterns and corresponding radiation patterns to address the particularities of any given wireless environment. Such a solution should take into account not only causes of interference but also the physical position and configuration of the transmitting or receiving device.